A LED, is a common component adopted in daily appliances due to advantages such as small size, long service life, low driving voltage, low power consumption, quick response, and good shock resistance etc. A working LED light source will generate heat, a value of which is in proportion to its power value. Earlier LED devices had power limited to milliwatts due to manufacturing technology. In recent years, new technologies were developed to enhance the power of LED devices and thus products using more power, for example, more than 100 milliwatts, were developed and are referred to as a power LED. As power LEDs have been applied in the field of illumination, high power LEDs using power of over 1 W have been developed and gradually applied in various areas of illumination. The power LED will generate heat when working. After the LED light source has been working for a long time, its accumulated heat will result in a short lifetime and unstable product performance. In order to resolve the problem of heat dissipation of a LED chip when working, prior art power LEDs adopted complex encapsulation structures.
Common supporting substrates used in prior art high power LEDs can be divided into framework, ceramics substrate, etc. FIG. 1 shows an encapsulation structure of a framework type power LED, which includes a heat dissipation plate 102 in addition to an ordinary Plastic Leaded Chip Carrier (hereinafter referred to as a PLCC). The framework structure is characterized in that a white or black colloid 104 is plastic-sealed over a metal frame 103 to form a cavity, an electrode lead 103 and a heat dissipation plate 102 are fixed, a chip 105 and a heat sink 106 are mounted within a reflective cup of the heat dissipation plate 102, and an optical lens 108 is mounted on top of the framework.
FIG. 2 shows an encapsulation structure of a ceramics substrate type power LED. The power LED is mainly characterized in that a chip 201 is mounted on a ceramic substrate 202 with a circuit printed thereon, with the ceramic substrate 202 and its circuit together forming a structure of heat dissipation and an electric connection of LED. On the top of the ceramic substrate 202 is mounted a metal reflective cavity 203, which supports a lens 204 and forms an optical structure. The ceramic substrate has a complex manufacturing process, low production efficiency, high cost, and limited capability of heat dissipation, and thus limited room for power enhancement of LED devices based on the ceramic substrate.
As production scale of the power LEDs has been expanded and an application field of power LEDs extended, the weaknesses of the product structure mentioned above, such as complex processing, low production efficiency etc., have become critical.
In order to cut down manufacturing cost, there has been developed a support (i.e., substrate) of power LED by means of assembling a heat sink in a circuit plate. However, this kind of substrate has disadvantages such as complex structure, strict requirement of manufacture process, less reliability and bad heat dissipation, leading to relatively high manufacturing costs, less reliability and short lifetime of the power LEDs product.
For example, a PCT patent application WO2006104325 discloses assembling a heat sink, in which, as shown in FIG. 3, multiple layers of circuit plates (301, 302, 303, 304, 4 layers in total) with through holes are stacked together to form a cavity for assembling a heat sink 305. However, these layers of circuit plates need to be stacked, assembled and welded, and there is a strict requirement for position in the manufacturing process. Also, when welding of the stacked circuit plates, defects such as inveracious soldering and an unflat joint may occur, leading to high manufacturing cost, high processing difficulty and low production efficiency.
To overcome the problem of heat dissipation for a LED device, there is a solution of opening a hole in the heat dissipation plate and embedding a heat sink in the hole. For example, a Chinese patent CN1977399A discloses a solution, in which a LED substrate is obtained by means of assembling a heat sink 404 with a circuit board 403, as shown in FIG. 4, a through hole structure 401 of the circuit board 403 is combined with the heat sink 404, and the circuit board 403 or the heat sink 404 has a conical surface 402. This solution is not suitable for high power LED devices because of a lower heat dissipation capacity of the heat sink. During manufacture, the binding between the heat sink and the through hole is weak so that the heat sink can easily break off and is difficult to locate. This results in low reliability and bad heat dissipation. In addition, the machining process of a conical surface on the circuit board has bad consistency and thus product quality is hard to guarantee.
Furthermore, there is a problem of low production efficiency and high cost for mass production of LED products due to the complex structures of heat dissipation substrate of the power LED. Therefore, there is a need to develop a new product, which has high production efficiency, simple structure and low production cost, so as to meet demand of the booming market.